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Gibbon mentions Eormanric in his chapter XXV. of the Decline and Fall, and, in spite of chronological discrepancies, this Eormanric is probably identical with the one mentioned in Beowulf (Chapter XVIII.), in Jornandes (Chapter XXIV.), and in the Edda. 
In Jornandes the story is as follows.
2. A Chief of the Roxolani tribe who was a traitor.
3. Sanielh (= Swanhild) wife of the chief.
4. Sarus, brothers of Sanielh.
Ermanaric puts Sanielh to death by causing her to be torn to pieces by wild horses, because of the treachery of her husband, the chief of the Roxolani. Her brothers, Ammius and Sarus, avenge her death by attacking Ermanaric, but they only succeed in wounding him and disabling him for the rest of his life.
In the Edda the story is as follows.
1. Gudrun, widow of Sigurd and Atli.
2. Swanhild, daughter of Gudrun by Sigurd.
3. Jonakur, Gudrun s third husband.
4. S�, sons of Gudrun and Jonakur.
7. Jormunrek (Eormanric).
8. Randver, son of Jormunrek.
Jormunrek hears of the beauty of Swanhild and sends his son Randver to seek her out for him in marriage. Gudrun consents; on the way Randver is incited by the traitor Bicci to betray Swanhild, and is then accused by him to the king. For this treachery Jormunrek hangs Randver and causes Swanhild to be trampled to death by wild horses. Then the three sons of Gudrun set out to avenge their sister. On the way his two brothers kill Erp, and are consequently unable to kill Jormunrek. They only succeed in maiming him.
Saxo Grammaticus, to whom we also owe the story of Hamlet, tells a similar story.
1. Jarmeric, a Danish King.
2. Swawilda (= Swanhild), wife of Jarmeric.
3. Hellespontine brothers, brothers of Swawilda.
4. Bicco, a servant of Jarmeric.
Bicco accuses Swawilda to Jarmeric of unfaithfulness. He causes her to be torn to pieces by wild horses. Then her brothers kill Jarmeric with the help of a witch, Gudrun, hewing off his hands and feet.
These three stories are evidently based on one common original.